Pancreatic juice is a fluid secreted from the exocrine portion of the pancreas into the duodenum of the small intestine. It has been used to detect gastrointestinal infection, bicarbonate levels, and to search for possible biomarkers for pancreatic cancer, as currently pancreatic cancer is not found in early stages and, when detected in advanced stages, has a poor prognosis.
S100P (S100 calcium binding protein P) is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are implicated in the regulation of cellular processes such as cell cycle progression and differentiation. S100P is a receptor for advanced glycation end products (RAGE) in pancreatic cancer and is associated with growth and invasion of pancreatic cancer. For example, it has been reported in Ohuchida et al., Clinical Cancer Research, 2006, Vol. 12, No. 18, pp. 5411-5416, that S100P represents a potential early marker of pancreatic cancer, and analysis of S100P concentration in pancreatic juice is useful for discriminating between tumor and chronic pancreatitis. It has further been reported in Nakata et al., Human Pathology, 2010, Vol. 41, pp. 824-831, that expression of S100P is not observed in normal pancreatic ductal epithelium, but is observed in intraductal papillary mucinous tumor cells. This suggests that S100P could represent a marker for pancreatic cancer, and measurement of S100P in pancreatic juice is expected to be useful for early detection, diagnosis, and/or staging of pancreatic cancer.
Pancreatic juice contains various digestive enzymes that are present in inactive form in the pancreas, but are activated after excretion into the duodenum. A cascade degradation reaction of digestive enzymes in pancreatic juice is initiated by enterokinase secreted from duodenal epithelial cells. Specifically, trypsinogen in pancreatic juice is converted into its active trypsin form by enterokinase, which then activates digestive enzymes/proteases such as chymotrypsinogen and proesterase. In the presence of these activeproteases, biological molecules such as proteins, nucleic acids, lipids, and cells contained in pancreatic juice are degraded or modified after excretion into the duodenum. Therefore, it may be difficult to determine the levels of biological molecules in a sample of pancreatic juice excreted into the duodenum, due to the influence of proteases and digestive enzymes in the biological sample.